Lose weight by building muscle
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Gretchen Reynolds on the science of fitness.
If there is a holy grail of weight loss, it would be a program that allows someone to shed fat rapidly while hanging on to or even augmenting muscle. Ideally, it would also be easy.
A new study describes a workout and diet regimen that accomplishes two of those goals remarkably well. But it may not be so easy.
For most of us, losing weight and keeping it off is difficult. If you consume fewer calories than your body requires for daily operations, it turns to internal sources of fuel. Those sources consist of body fat and lean tissue, meaning muscle. When someone on a diet drops a pound of body mass (a measure that does not include water), much of that pound consists of fat. But about a third or more can be made up of muscle.
The problem with losing muscle is that, unlike fat tissue, muscle burns calories. Having less muscle means a lower resting metabolic rate, so you burn fewer calories throughout the day. Losing muscle may also discourage physical activity, which is important for maintaining weight loss.
So researchers have long been looking for weight loss programs that produce hefty amounts of fat loss but diminish any decline in muscle.
For scientists at McMaster University in Ontario, Canada, that goal seemed to demand a high dose of protein and also plenty of exercise.
As the scientists knew, amino acids in protein help muscle tissue to maintain itself and to grow. Many past studies have suggested that low-calorie but high-protein diets can result in less muscle loss than the same number of calories but less protein.
However, the best dosage of protein in these circumstances has remained unclear, as has the role, if any, for exercise.
So for the new study, which was, the McMaster researchers rounded up 40 overweight young men who were willing to commit to an intensive weight-loss program and divided them in half.
All of the young men began a diet in which their daily calories were cut by about 40 percent (compared to what they needed to maintain weight). But for half of them, this consisted of about 15 percent protein, 35 percent fat and 50 percent carbohydrates.
The other 20 volunteers began a diet that mimicked that of the first group, except that theirs swapped the protein and fat ratios, so that 35 percent of their calories came from protein and 15 percent from fat. Over all, their protein intake was about three times the recommended dietary allowance for most people.
The researchers handled that switch by changing the make-up of a supplied drink. In the low-protein group, the beverage contained high-fat milk and no added protein. For the others, it consisted of low-fat milk and a large dollop of whey protein.
All of the men also began a grueling workout routine. Six days a week they reported to the exercise lab and completed a strenuous full-body weight training circuit, high-intensity intervals, or a series of explosive jumps and other exercises known as plyometric training.